As luck would have it -- and luck had a starring role on this peculiar night -- everything went according to plan. Which is to say, there was no plan, and that turned out to be just fine. Better than fine; amazing. Wonderful. Revealing and provocative. It had all the markings of a fiasco -- unrelated elements brought together for the first time only at the performance, their order determined by chance rather than Cunningham's dictates. But once again, Cunningham's wisdom in extending the performance beyond his own imagination was affirmed. Chance was good to him, and he was good to us.

It was a fitting tribute to the Cunningham company's half-century of revealing, provocative and deeply peculiar performances.

Yes, Merce Cunningham invited two experimental rock bands, Radiohead and Sigur Ros, to write and perform music for his latest choreography, "Split Sides." No, this premiere for the Merce Cunningham Dance Company's 50th anniversary gala at the Brooklyn Academy of Music on Tuesday night did not turn into a rock concert with dancers.

As many a guest collaborator has learned, there is no way to upstage Merce Cunningham, pope of the dance avant-garde, or his work. Good sports, Radiohead from Britain and Sigur Ros from Iceland were relegated to an atypical role as pit musicians. Somewhat tame in the Cunningham context, barely seen but certainly heard, they implicitly agreed that the emphasis was on the dancers onstage above them.

Still, to paraphrase a line from "Hamlet," what's rock music to Merce or he to rock? The answer was not easy to find, although an aura of risk hung festively in the air as the evening opened with Mayor Michael R. Bloomberg praising Mr. Cunningham on the same stage. Past collaborators — including the painters Jasper Johns and Robert Rauschenberg — stood by and the musicians, lined up, looked amused and somewhat perplexed as dancers jumped up and down or fell to the floor behind them during the speeches. Typical Cunningham simultaneity and assemblage.

At the Merce Cunningham Dance Company’s recent show at the Brooklyn Academy of Music, the average age of Cunningham’s audience seemed to have dropped by about thirty years, and that is because the troupe, normally a rather egghead enterprise, chose to perform to rock music this season. Cunningham was one of the creators of America’s mid-century modernism, as, more famously, was his lifelong collaborator, John Cage, who died eleven years ago. Accordingly, the Cunningham company, for most of its history, has performed to the sort of arrhythmic, ametric, amelodic “new music” that Cage and his cohort produced: somebody making electronic static, somebody shaking beans in a jar, somebody mumbling into a mike. So when it was announced that the big new piece this season, the company’s fiftieth, would be accompanied by two rock bands—Radiohead, the very hot British ensemble, and Sigur Rós, from Iceland—there was considerable head-scratching. Were Cunningham’s dancers going to perform to something as normal as song? Were they going to dance to a beat? Why use rock anyway? Trevor Carlson, the company’s general manager and the person whose idea this was, told the Times why: to bring in people previously unexposed to the company—in other words, to sell Cunningham to the young.

Rolling the dice gives a moment of wonder, the imagination conjuring. A split-second later, the dice at rest, the mind becomes active.— Merce Cunningham

Of all of the multiple innovations in the work of Merce Cunningham, the use of chance is the most confusing. Such a clear thing, this toss of a die, or a handful of pennies, and yet chance is the Holy Ghost of Dance—the part of the Cunningham Trinity taken on faith, and dimly apprehended. The independence of dance as an art form–the notion that dance does not need music, but may simply coexist with it—still may seem heresy to some, but as an idea it is well understood. The separation of dance from story is now old hat, or old enough, though still giving rise to the notion that Cunningham's dances are "abstract," when dance, because it is done by people, can never really be abstract. But chance! Chance makes people think of randomness, of disorder, of improvisation, of fate and fortune, of things made up as they are happening, or just before. Nothing, though, could be further from the Merceian truth, which is quite the opposite. His is not the unhinged Miltonic world of Paradise Lost, where "Chaos umpire sits," and "Chance governs all." Not in the slightest. In his world, Merce governs all, even when by a kind of non-doing, this latter being neither benign nor malign, but a kind of sovereign absenting of ego. Even when Cunningham does not make choices—as when, for instance, he leaves the decor to the art director, or some similar personage, who chooses the artists; and likewise hands off the music—he has chosen the chooser. The truth is that in his world, Cunningham is God. Every choice, or non-choice, is made by him.

In the chance procedures Cunningham uses at some point in the making of each of his dances, all the available elements are his. This movement first, or that one? The moves are all his. What number of dancers? The number available is up to him. Chance is simply a marvelous surprise-generator. And Cunningham likes surprises. Thus he must have enjoyed his season this past week at the Brooklyn Academy of Music, where chance procedures went public.

Paradox envelops Merce Cunningham and his stature as the most renowned American choreographer alive today.

At 84, he is very much the grand old man of dance. His revolutionary movement and its concert trappings are hallmarks of the mid-20th Century avant-garde. His name is synonymous with bold experimentation married to unimpeachable high standards.

And therein lies the amusing rub: Unlike most octogenarian artists still in high repute, Cunningham, whose troupe performs Friday and Saturday at the new Joan W. and Irving B. Harris Theater, in no way stands for nostalgia or cuddly, old-fashioned favorites. He and his collaborators -- composer John Cage and visual artist Robert Rauschenberg most notably -- so pushed the art of dance to the limits that it's nearly impossible to think of them as sacred or classic.